Pollution: UPSC Previous Year Questions (Environment and Ecology)

Explanation

Waste-to-Energy (WTE) technologies consist of any waste treatment process that creates energy in the form of electricity or heat from several types of waste: from the semi-sol-id (e.g. thickened sludge from effluent treatment plants) to liquid (e.g. domestic sewage) waste. Landfill gas recovery, Gasification, Pyrolisis, Thermal Depolymerisation are examples of Waste-to-Energy (WTE) technologies.

Option (d) is correct: Pyrolysis is a process of chemical de-composition of organic matter brought about by heat. In this process, the organic material is heated in the absence of air until the molecules thermally break down to become a gas comprising smaller molecules (known collectively as syngas). Gasification can also take place as a result of partial combustion of organic matter in the presence of a restricted quantity of oxygen or air. The gas, so produced, is known as producer gas. The gases produced by pyrolysis mainly comprise carbon monoxide (25%), hydrogen and hydrocarbons (15%), and carbon dioxide and nitrogen (60%). It is used commercially as a waste to energy system that converts municipal solid waste into synthesis gas (syngas) containing hydrogen and carbon monoxide that can be used to generate power.

Explanation

Microbeads are manufactured solid plastic particles of less than one millimetre in their largest dimension. They are most frequently made of polyethene but can be of other petrochemical plastics such as polypropylene and polystyrene. They are used in exfoliating personal care products, toothpaste and in biomedical and health-science research.

Option (a) is correct: Microbeads can cause plastic particle water pollution and pose an environmental hazard for aquatic animals in freshwater and ocean water. NGT had earlier directed the GoI to test cosmetic products containing microbeads after a plea sought a ban on their use on the ground they are extremely dangerous for aquatic life and the environment.

Explanation

Methane hydrate is an ice-like substance formed when CH₄ and water combine at low temperature (up to 250C) and moderate pressure (greater than 3-5 MPa, which corresponds to combined water and sediment depths of 300 to 500 m).

Statement 1 is correct: Owing to the melting of ice, global warming might trigger the release of methane gas from these deposits hence having a significant impact on climate change.

Statement 2 is correct: Sediment and sedimentary rock units below Arctic permafrost have the temperature and pressure conditions suitable for the formation and stability of methane hydrate.

Statement 3 is correct: Methane is relatively short-lived in the atmosphere; a molecule of methane is oxidised to water and carbon dioxide within a decade or so, mainly by reaction with other trace gases.

Explanation

Burning stubble (parali) is the process of removing crop residue from the field in order to prepare it for the next crop. Open stubble burning releases a lot of harmful pollutants into the air, including smoke, particles, greenhouse gases (CO₂, N₂O, O₃ CH₄), air pollutants (CO, NH₃, NOx, SO₂, NMHC), and volatile organic compounds. These pollutants are dangerous to human health. Husk burning reduces the fertility of the soil by destroying its nutrients. When stubble burns, heat is produced that permeates the soil, causing the loss of moisture and beneficial microbes.